This invention relates to a brake device equipped hydraulic motor which is suitable for use, for example, as a hydraulic motor of a rotary drive mechanism or vehicular drive mechanism of a excavator or the like.
Illustrated by way of example in FIGS. 8 through 13 is a prior art brake device equipped hydraulic motor which is applied as a hydraulic motor of a excavator rotary mechanism.
In these figures, indicated at 1 is a vehicular lower body, at 2 an upper rotary body which is rotatably mounted on the vehicular lower body 1. Provided on the upper rotary body 2 is a frame 3 to support thereon a cab 4, a housing cover 5 which internally defines a machine room and a counterweight 6. Further, provided on a front portion of the upper rotary body 2 is a front working mechanism 7 with a member to be lifted up and down, for example, to perform an excavating operation. Being rotationally driven from a hydraulic motor 10 as described below, the upper rotary body 2 is rotated relative to the vehicular lower body 1.
The hydraulic motor 10 of a rotary body drive mechanism (hereinafter referred to simply as xe2x80x9chydraulic motorxe2x80x9d) is mounted on the rotary frame 3 of the upper rotary body 2 through a reducer (not shown), and, as described below, largely constituted by a casing 11, output shaft 14, cylinder block 15 and a brake device 22.
As shown in FIG. 9, the casing 11 of the hydraulic motor 10 is constituted by a main casing body 12 of a stepped tubular shape provided with a cylindrical portion 12A and bottom portion 12B which is closed at a bottom end thereof, and a head casing 13 which is adapted to close the other open end of the main casing body 12. Further, the main casing body 12 is provided with an annular flange 12C around an outer periphery of its bottom portion 12B. The casing 11 is disposed in a vertical direction, and the flange 12C at its lower end is integrally fixed to a reducer.
Furthermore, on the inner peripheral side, the main casing body 12 is provided with a couple of stepped portions 12D and 12E by which the inside diameter of the main casing body 12 is increased stepwise toward its open end. Provided on the stepped portion 12 are a large number of coupling grooves 12F (only two of which are shown in the drawing) at intervals around the inner periphery or in the circumferential direction for engagement with non-rotating brake disks 23 which will be described hereinafter.
Indicated at 14 is an output shaft which is rotatably supported in the casing 11. More specifically, the output shaft 14 is rotatably supported by the main casing body 12 through a bearing 14A in the vicinity of its bottom portion 12B and at the same time by the head casing 13 through a bearing 14B.
Denoted at 15 is a cylinder block which is provided within the casing 11. The cylinder block 15 is splined with and supported on the output shaft 14. In this instance, a plural number of cylinders 16 are formed axially in the cylinder block 15 in angularly spaced positions around the circumference of the output shaft 14. To and from the cylinder block 15, operating oil is supplied from outside through inlet/outlet ports 18A and 18B, which will be described hereinafter, thereby to rotationally drive the output shaft 14.
Indicated at 17 are, for example, nine arcuate grooves which are provided on the outer peripheral side of the cylinder block 15. These arcuate grooves 17 are each in the form of a semi-circular groove which is extended in the axial direction of the cylinder block 15 and located substantially in equidistant positions around the circumference of the cylinder block 15. In this instance, as shown in FIG. 12, the arcuate grooves 17 are formed in a predetermined radius of curvature R1 which is, for example, approximately 10.00 mm.
Designated at 18 is a valve plate which is provided between the head casing 13 and the cylinder block 15 and fixed to the head casing 13. This valve plate 18 is provided with a pair of inlet/outlet ports 18A and 18B which are intermittently communicated with the respective cylinders 16 of the cylinder block 15. These inlet and outlet ports 18A and 18B are communicated with an oil supply passage (not shown) which is formed on the side of the head casing 13.
Indicated at 19 are a plural number of pistons each having one end portion (an upper end portion) slidably fitted in a cylinder 16 of the cylinder block 15 and having the other end portion (a lower end portion) projected to the outside of the cylinder 16. Each piston 19 is provided with a shoe 20 rockably at the projected lower end.
Denoted at 21 is a swash plate which is fixedly provided in the main casing body 12. The pistons 19 are reciprocated into and out of the cylinders 16 as the shoes 20 of the respective pistons 19 are caused to slide on the upper side of the wash plate 21.
Indicated at 22 is a negative type brake device which is provided for applying brakes to the output shaft 14 and the cylinder block 15. This brake device 22 is constituted by non-rotating brake disks 23, rotating brake disks 24, a brake piston 27 and so forth, as described below.
Indicated at 23 are the non-rotating brake disks which are provided on the inner peripheral side of the main casing body 12 between the stepped portions 12D and 12E. These non-rotating brake disks 23 are each in the form of an annular disk using a friction material and, on the outer peripheral side, are engaged with the coupling grooves 12F of the main casing body 12. Consequently, the non-rotating brake disks 23 are axially movable relative to the main casing body 12 but blocked against rotation relative to the latter.
Designated at 24 are the rotating brake disks which are provided on the outer peripheral side of the cylinder block 15. As shown in FIG. 10, the rotating brake disk 24 are each in the form of an annular disk using a friction material (lining), and are located on the outer peripheral side of the cylinder block 15 in an alternately overlapped state with the non-rotating brake disks 23.
By way of arcuate projections 25 which will be described below, the rotating brake disks 24 are made movable in the axial direction relative to the cylinder block 15, and can be brought into friction engagement with the non-rotating brake disks 23 to apply brakes to the cylinder block 15 in cooperation with the non-rotating brake disks 23.
Indicated at 25 are nine arcuate projections which are provided on the inner peripheral side of each rotating brake disk 24 and projected radially inward in an arcuate shape, from uniformly spaced angular positions on the inner periphery of the rotating disk 24. These arcuate projections 25 are engaged with the arcuate grooves 17 on the side of the cylinder block 15 to restrict movements of the rotating brake disks 24 in rotational directions relative to the cylinder block 15.
In this instance, as shown in FIG. 12, the arcuate projections 25 are formed in a predetermined radius of curvature R2 which is slightly smaller than the radius of curvature R1 of the above-mentioned arcuate grooves 17 and which is, for example, approximately 9.75 mm.
Designated at 26 are nine grooves which are formed between adjacent arcuate projections 25 and are located in equidistant positions on the inner periphery of each rotating brake disk 24 alternately with the arcuate projections 25.
Indicated at 27 is a brake piston which is axially slidably fitted in the main casing body 12. This brake piston 27 is formed in a stepped cylindrical shape to define a liquid pressure chamber 28 in association with the stepped portion 12E of the main casing body 12. Further, under the influence of biasing action of a spring 29, the brake piston 27 is constantly urged toward the non-rotating and rotating brake disks 23 and 24. Consequently, the non-rotating and rotating brake disks 23 and 24 are held in frictional engagement with each other by the brake piston 27, and the cylinder block 15 is retained in a braked state together with the output shaft 14 by application of the so-called parking brake.
Further, the casing 11 is provided with a liquid passage (not shown) which is communicated with the above-mentioned liquid pressure chamber 28. When part of pressure oil from a hydraulic pump (not shown) is supplied to the liquid pressure chamber 28 through the liquid passage, the brake piston 27 moved away from the non-rotating brake disks 23 to take the brake off the cylinder block 15.
In the case of the prior art hydraulic motor 10 of this sort, pressure oil from a hydraulic pump is successively supplied to the respective cylinders 16 through the inlet/outlet ports 18A and 18B of the valve plate 18, thereby generating pressures to push the pistons 19 against the swash plate 21 through the shoes 20. Accordingly, the shoes 20 are caused to slide on the swash plate 21 in the circumferential direction, and as a result the cylinder block 15, which is integrally assembled with the pistons 19, is put in rotation. At this time, the rotational force is transmitted to a reducer through the output shaft 14 to rotate the upper rotary body 2 on and relative to the vehicular lower body 1.
When the hydraulic motor 10 is in operation in this manner, part of pressure oil from a hydraulic pump is also supplied to the liquid pressure chamber 28, causing the brake piston 27 to displace in an upward direction in FIG. 9 against the action of the spring 29 to take the brakes off the cylinder block 15.
On the other hand, at the time of stopping the hydraulic motor 10, the supply of pressure oil to the liquid pressure chamber 28 is turned off, whereupon the brake piston 27 is pushed by the spring 29 toward the non-rotating brake disks 23 to bring the non-rotating brake disks 23 on the side of the casing 11 into frictional engagement with the rotating brake disks 24 on the side of the cylinder block 15 to stop the rotation of the latter.
According to the above-described prior art, at the time of stopping the hydraulic motor 10, the non-rotating and rotating brake disks 23 and 24 are forcibly pressed together against the casing 11 by the brake piston 27, and as a result non-rotatably fixed to the casing 11 which is integrally mounted on the upper rotary body 2.
However, in the case of the prior art, substantially a small gap space exists between the arcuate grooves 17 on the cylinder block 15 and the arcuate projections 25 on the rotating brake disks 24 as shown in FIG. 12. Therefore, when the brake device 22 is actuated to apply the brakes on the cylinder block 15 to stop a rotational movement of the upper rotary body 2, the so-called xe2x80x9cback swingingxe2x80x9d motions may occur to the upper rotary body due to its repeated forward and reverse inertial rotations. In such a case, the arcuate projections 25 of the rotating brake disks 24, which are fixed to the casing 11 as mentioned hereinbefore, are repeatedly hit against the arcuate grooves 17 of the cylinder block 15 which is connected to the side of the vehicular lower body 1 through a reducer, to suffer from abrasive wear as shown in FIG. 13.
Besides, when traveling on an unlevel ground, backlashing or saccadic movements may occur, for example, to meshed gears of the reducer or to mechanical components on the side of the front working mechanism, causing the arcuate projections 25 of the rotating brake disks 24 to hit against the arcuate grooves 17 of the cylinder block 15 frequently and repeatedly to suffer from accelerated abrasive wear.
With progress of the abrasive wear of the arcuate projections 25 as described above, the gap spaces between the arcuate projections 25 and the arcuate grooves 17 are widened to increase the impact of collision and the abrasive wear of the arcuate projections 25 all the more. In some cases, the arcuate projections 25 are worn out or damaged totally or to such a degree as to impair the braking functions.
In addition, since the hydraulic motor 10 is disposed vertically, lower ones of the rotating brake disks 24 are subjected to all the weights of the rotating and non-rotating brake disks 24 and 23 which are in upper positions.
Therefore, when applying the brakes to the hydraulic motor 10, an extremely large inertial force is exerted on lower ones of the rotating brake disks 24 to increase the impacts of collision of the arcuate projections 25 of the rotating brake disks 24 against the arcuate grooves 17 of the cylinder block 15 and thus to increase the degree of abrasive wear of the arcuate projections 25.
Further, dust which results from abrasion of the arcuate projections 25 could get onto sliding parts of the hydraulic motor 10 to cause problems such as galling or seizure of the sliding parts which would invite degradations in performance quality of the hydraulic motor 10.
In this connection, it is possible to suppress abrasive wear of the rotating brake disks to some extent by increasing contact areas with the cylinder block, more specifically, by providing flat spline grooves on the cylinder block 15 in place of the arcuate grooves 17 while providing on the rotating brake disks flat projections, in place of the arcuate projections 25, for fitting engagement with the grooves.
However, in such a case, it becomes necessary to form spline grooves on the cylinder block by a machining operation using a hobbing machine or the like, which is time consuming and could drop production efficiency to a material degree.
In view of the above-mentioned problems with the prior art, it is an object of the present invention to provide a brake device equipped hydraulic motor, which is arranged to suppress abrasive wear of rotating brake disks to a sufficiently low level at the time of application of the brakes to maintain satisfactory braking performance quality over a long period of time, while precluding causes of abrasion and galling of sliding parts and guaranteeing facilitated machining operations.
In order to solve the above-mentioned problems, according to the present invention, there is provided a brake device equipped hydraulic motor of the type which basically includes a casing formed generally in a tubular shape, an output shaft rotatably supported in the casing, a cylinder block provided in the casing and supplied with pressure oil from outside to rotationally drive the output shaft, and a brake device provided between the cylinder block and the casing to apply brakes to the output shaft, the brake device having annular non-rotating brake disks provided on inner peripheral side of the casing, annular rotating brake disks provided axially movably on outer peripheral side of the cylinder block in alternately overlapped relations with the non-rotating brake disks adapted to be brought into frictional engagement with the non-rotating brake disks by a brake piston.
The brake device equipped hydraulic motor according to the present invention is characterized by the provision of: a plural number of axially extending arcuate grooves provided on circumferential surfaces of the cylinder block at predetermined angular intervals in a circumferential direction thereof; a plural number of arcuate projections provided on inner peripheral side of and extended radially inward of the rotating brake disks and engaged with the arcuate grooves to restrict rotational movements of the rotating brake disks relative to the cylinder block; and at least three radial contacting land portions each located between said arcuate projections and arranged to be brought into contact circumferential surfaces of the cylinder block to restrict radial movements of the rotating brake disks relative to the cylinder block.
With the arrangements just described, at the time of braking the hydraulic motor, a plural number of rotating brake disks which are provided on the side of the cylinder block are pushed into frictional engagement with a plural number of non-rotating brake disks by a brake piston of the brake device thereby to stop rotation of the cylinder block. At this time, the arcuate projections which are projected on the inner peripheral side of the rotating brake disks are engaged with arcuate grooves on the circumferential surfaces of the cylinder block to restrain rotational movements of the rotating brake disks relative to the cylinder block.
Besides, at the time of application of the brakes, the radial contacting land portions which are provided on the inner peripheral side of the rotating brake disks are brought into contact with circumferential surfaces of the cylinder block to restrict radial movements of the rotating brake disks relative to the cylinder block. Accordingly, the radial contacting land portions contribute to ease the impacts of collision as the arcuate projections are collided against the arcuate grooves of the cylinder block in radial directions.
Further, according to the present invention, the radial contacting land portions are formed in an arcuate shape conforming with contour of the circumferential surfaces of the With the arrangements just described, when the rotating brake disks tend to move in a radial direction relative to the cylinder block upon application of the brakes, the radial contacting land portions are brought into contact with circumferential surfaces of the cylinder block, preventing the arcuate projections from directly colliding against the arcuate grooves in a radial direction.
Further, according to the present invention, in addition to the arcuate projections and radial contacting land portions, the rotating brake disks are provided with grooves deeper than the radial contacting land portions, providing oil passages between the grooves and the circumferential surfaces of the cylinder block.
With the arrangements just described, for example, as oil is fed to and from the cylinder block, leaked oil in the casing can find escape passages to the outside through the oil passages which are formed between the grooves of the rotating brake disks and the cylinder block. Accordingly, this prevents the oil pressure in the casing from rising to an unnecessarily high level.
On the other hand, according to the present invention, there is also provided a brake device equipped hydraulic motor which basically includes a casing formed generally in a tubular shape, an output shaft rotatably supported in the casing, a output shaft provided in the casing and supplied with pressure oil from outside to rotationally drive the output shaft, and a brake device provided between the output shaft and the casing to apply brakes to the output shaft, the brake device having annular non-rotating brake disks provided movably on inner peripheral side of the casing, annular rotating brake disks provided on outer peripheral side of the output shaft in alternately overlapped relations with the non-rotating brake disks adapted to be brought into frictional engagement with the non-rotating brake disks by a brake piston.
In this case, according to the present invention, the brake device equipped hydraulic motor is characterized by the provision of: a plural number of axially extending arcuate grooves provided on circumferential surfaces of the output shaft at predetermined angular intervals in a circumferential direction thereof; a plural number of arcuate projections provided on inner peripheral side of and extended radially inward of the rotating brake disks and engaged with the arcuate grooves to restrict rotational movements of the rotating brake disks relative to the output shaft; and at least three radial contacting land portions each located between the arcuate projections and arranged to be brought into contact circumferential surfaces of the output shaft to restrict radial movements of the rotating brake disks relative to the output shaft.
With the arrangements just described, at the time of braking the hydraulic motor, the radial contacting land portions which are provided on the inner peripheral side of the rotating brake disks are engaged with circumferential surfaces of the output shaft thereby to restrict radial movements of the rotating brake disks relative to the output shaft in a manner similar to the above-described first preferred form of the invention, contributing to ease the impact of collision between the arcuate projections and the arcuate grooves of the output shaft.
Further, according to the present invention, the radial contacting land portions are formed in an arcuate shape conforming with contour of the circumferential surfaces of the output shaft, and arranged to face the circumferential surfaces of the output shaft through a small gap space narrower than a gap space between the arcuate grooves and arcuate projections.
With the arrangements just described, when the rotating brake disks tend to move in a radial direction relative to the output shaft upon applying the brakes, the radial contacting land portions are brought into contact with circumferential surfaces of the output shaft to prevent the arcuate projections from directly colliding against the arcuate grooves in radial directions.
Further, according to the present invention, in addition to the arcuate projections and radial contacting land portions, the rotating brake disks are provided with grooves deeper than the radial contacting land portions, providing oil passages between the grooves and the circumferential surfaces of the output shaft.
With the arrangements just described, for example, as oil is fed to and from the cylinder block, leaked oil in the casing can find escape passages to the outside through the oil passages which are formed between the grooves of the rotating brake disks and the cylinder block. Accordingly, this prevents the oil pressure in the casing from rising to an unnecessarily high level in a manner similar to the above-described third preferred form of the invention.
Furthermore, according to the present invention, the arcuate projections are formed in a slightly smaller radius of curvature as compared with the arcuate grooves. This arrangement permits to assemble the arcuate projections with the arcuate grooves in a facilitated manner in an assembling stage.